1. Field of the Invention
The invention relates to catalytic systems, consisting of an active part and inert component and intended for the oxidative demercaptanization (sweetening) of hydrocarbon compositions including petroleum, petroleum distillates, gasolines, kerosenes, jet fuels, diesel fuels and heating oils, natural-gas liquids, etc., processes for the production of the catalysts, and their use in the field mentioned above.
2. Description of the Prior Art
The oxidative demercaptanization (sweetening) of hydrocarbon compositions (e.g. petroleum distillates, fuels etc.) is well known and widely practiced process for removal of poor smelling, toxic and corrosive mercaptans and related substances. Said process is based on the oxidation of mercaptans with the formation of innocuous disulphides. Processes where the hydrocarbons have been treated by oxygen or oxygen-containing gas in the presence of homogeneous or heterogeneous metal-complex catalysts and alkaline agent (more often aqueous caustic), e.g., well known UOP MEROX process, have obtained the greatest distribution.
Catalyst for the oxidative demercaptanization should satisfy to the following main requests:    provide decrease of mercaptan sulphur concentration in the treated products to an tolerance level (usually 3–10 ppm);    stable work during long time;    not pollute a product by harmful impurities;    not contain expensive and poison components;    hydrocarbon compositions mustn't change their colour or become less stable after the treatment.
Besides, it is desirable that the catalyst could be easily regenerated.
A commonly used catalyst for alkaline sweetening is cobalt phthalocyanine (see for example European patent-394571, German patent 3008284 etc.). Use of alkalies complicates the technology because of an occurrence of additional operations on the separation of water and organic phases and the clearing of waste water. Attempts to create effective non-alkaline process therefore do not cease.
A rather large number of catalysts and catalytic compositions for non-alkaline demercaptanization is known on the basis of connections of transitive metals. It was offered to use:    chelate complexes including porphyrinates of transition metals (Co, Cu, V a.o., European patent 0252853);    complexes of transition metals (e.g. Co, Cu, Ni, Fe) with three- or tetradentate ligands containing at least one amide group (French patent 2573087);    phthalocyanines of transition metals (U.S. Pat. No. 4,159,964),    complexes of transition metals with cation-exchange resins (British patent 1167017);    products of reactions between transition metal salts and tetracyanothiophene or tetracyanodithiine (French patent 2591610);    cupric salts, e.g. cupric chloride, in a combination with organic acids, alkyl amines, alkanol amines, amino acids, or urea derivatives (British patent 996500).
Various oxides are often applied as inert components (supports) for heterogeneous catalysts. For example, silica, alumina, alumosilicates, zeolites are listed in French patent 2591610. The use of Si, Al, Zr, Th oxides and products of their combination with oxides of silicon and other elements, for example, kaolin, montmorillonite, etc., were pointed out in European patent 0252853. An active carbon, frequently with various additives, is another widespread carrier. So, active carbon, modified by phosphates, e.g., ammonium phosphates, is offered in British patent 996500 as an inert component.
There is no mention in the prior art that combinations of transition metal oxides and complexes of transition metal salts with organic compounds would be effective catalytic systems for the oxidative demercaptanisation. Quite surprisingly we have found that such combinations of nitrogen-containing organic compounds gave excellent results. Thus, the present invention provides a new catalytic composition, the method of its production and its use in the oxidative demercaptanization.